294
UNIT 3
Organ Systems
Figure 15-12B.
Goblet cells, columnar absorptive cells, and microvilli.
EM, (
left
, large intestine)
3
4,831, (
right
, small intestine)
3
6,906
There are numerous
mitochondria
in the apical cytoplasm of the
columnar absorptive cells
.
Junction complexes
are located between
neighboring cells near the lumen, and
microvilli
are present on the apical surfaces of the
absorptive cells
. A
goblet cell
with many
mucus-secretory granules
in the cytoplasm is also shown here. These granules contain
mucinogen
and are released onto the
surface
of the epithelium by
exocytosis
. During exocytosis, mucinogen becomes hydrated and forms mucin, which expands greatly in
volume after it is released from the goblet cell.
Mucus (mucinogen) granules
Goblet cell
Microvilli
Microvilli
Microvilli
Tight junctions
Tight junctions
Tight junctions
Desmosome
Desmosome
Desmosome
Mitochondria
Mitochondria
of absorptive cells
of absorptive cells
Mitochondria
of absorptive cells
Absorptive cells
Absorptive cells
Absorptive cells
Microvilli
Microvilli
Microvilli
B
Goblet
Goblet
cells
cells
Goblet
cells
Columnar
Columnar
absorptive
absorptive
cells
cells
Columnar
absorptive
cells
Microvilli
Microvilli
Microvilli
A
Figure 15-12A.
Columnar absorptive and goblet cells of
the small intestine.
H&E,
3
1,422
The
columnar absorptive cells
of the small intestine are also
called
enterocytes
or
intestinal absorptive cells
. They are tall
and columnar in shape; oval-shaped nuclei lie in the basal
region of the cells. The columnar absorptive cells are the
predominant cells in the epithelium of the small intestine.
The apical surfaces of the cells are covered by
microvilli
,
which are coated with
glycocalyx
. The microvilli increase
the cellular surface area for absorption.
Goblet cells
are
interspersed among the absorptive cells. These are
unicellu-
lar glands
(see Fig. 3-20A,B) with a distinctive goblet shape.
The goblet cells are mucus-secreting cells, and their numbers
gradually increase from the proximal (duodenum) to the dis-
tal (ileum) portions of the small intestine.
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